In the pharmaceutical field, great efforts are being made to minimize the toxicological potential of pharmaceutical agents. Among the risks associated with exposure to toxic agents is the possibility of causing injury or death to cells of the body, which can result in damage to vital organs.
Mandel and Metais (1948) reported the discovery of extracellular nucleic acids in human plasma.
Lo, K. W. et al. (1990) and Kopreski, M. et al. (1999) have both reported the detection of tumor derived RNA in the plasma of cancer patients.
Chen, X. Q. et al. (2000) have proposed the use of telomerase RNA as a detection marker in the serum of breast cancer patients.
Poon, L. L. et al. (2000) have reported the presence of fetal RNA in maternal plasma.
U.S. Pat. No. 6,329,179 discloses the use of tumor-derived or associated extracellular RNA found circulating in the plasma or serum fraction of blood for the detection, monitoring, or evaluation of cancer or pre-malignant conditions.
U.S. Pat. No. 6,156,504 discloses the detection, identification, or monitoring of the existence, progression or clinical status of benign, pre-malignant, or malignant neoplasms in humans or animals that contain a mutation associated with the neoplasm through detection of the mutated nucleic acid of the neoplasm in plasma or serum fractions.
U.S. Pat. No. 6,020,124 discloses the detection of soluble DNA for mutated genes and oncogenes in biological fluids.
As RNA is considered to be labile, researchers have examined possible mechanisms by which RNA in human plasma is protected from degradation. Hasselmann, D. O. et al. (2001) have reported that in an in vitro model, mRNA within apoptotic bodies released by melanoma cells was protected from degradation when incubated in human serum.
Ng, E. K. O. et al. (2002) have reported that a substantial portion of plasma mRNA is particle-associated.
Tsui, N. B. Y., et al (2002) have examined the stability of endogenous and added RNA in blood, serum and plasma.
Conventional methods available for determining whether an agent causes tissue and cell damage include biochemical methods that measure markers of cell damage. For example, the enzymes, ALT, AST and 5′NT may be used as indicators of damage to liver cells (Duncan, J. R. et al. (1994). These enzymes, which are normally found in liver cells, are released when liver cells are damaged and may then be detected in the blood. However, the ability to use such indicators for early detection depends upon a number of factors, including the rapidity of enzyme release and the sensitivity of detection. Traditional methods are thus relatively insensitive and non-specific. Hence, there exists a growing interest to uncover additional early biological indicators or biomarkers of toxicity.